Dallas Semiconductor DS2252T-32-16, DS2252T-64-16 Datasheet

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DS2252T

Secure Microcontroller Module

FEATURES

 8051-compatible microcontroller for

secure/sensitive applications

- 32, 64, or 128 kbytes of nonvolatile SRAM for program and/or data storage

- In-system programming via on-chip serial port

- Capable of modifying its own program or data memory in the end system

 Firmware security features:

- Memory stored in encrypted form

- Encryption using on-chip 64-bit key

- Automatic true random key generator

- SDI (Self-Destruct Input)

- Improved security over previous generations

- Protects memory contents from piracy

 Crashproof operation

- Maintains all nonvolatile resources for over 10 years in the absence of power

- Power-fail Reset

- Early Warning Power-fail Interrupt

- Watchdog Timer

- Precision reference for power monitor

 Fully 8051-compatible

- 128 bytes scratchpad RAM

- Two timer/counters

- On-chip serial port

- 32 parallel I/O port pins

 Permanently powered real time clock

PACKAGE OUTLINE

1202140

40-Pin SIMM

DESCRIPTION

The DS2252T Secure Microcontroller Module is an 8051-compatible microcontroller based on nonvolatile RAM technology. It is designed for systems that need to protect memory contents from disclosure. This includes key data, sensitive algorithms, and proprietary information of all types. Like other members of the Secure Microcontroller family, it provides full compatibility with the 8051 instruction set, timers, serial port, and parallel I/O ports. By using NV RAM instead of ROM, the user can program, then reprogram the microcontroller while in-system. This allows frequent changing of sensitive processes with minimal effort. The DS2252T provides an array of mechanisms to prevent an attacker from examining the memory. It is designed to resist all levels of threat including observation, analysis, and physical attack. As a result, a massive effort would be required to obtain any information about

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DS2252T

memory contents. Furthermore, the “Soft” nature of the DS2252T allows frequent modification of secure information. This minimizes that value of any information that is obtained.

Using a security system based on the DS5002FP, the DS2252T protects the memory contents from disclosure. It loads program memory via its serial port and encrypts it in real time prior to storing it in SRAM. Once encrypted, the RAM contents and the program flow are unintelligible. The real data exists only inside the processor chip after being decrypted. Any attempt to discover the on-chip data, encryption keys, etc., results in its destruction. Extensive use of nonvolatile lithium-backed technology creates a microcontroller that retains data for over 10 years at room temperature, but which can be erased instantly if tampered with. The DS2252T even interfaces directly to external tamper protection hardware.

The DS2252T provides a permanently powered real time lock with interrupts for time stamp and date. It keeps time to one hundredth of a second using its onboard 32 kHz crystal.

Like other Secure Microcontrollers in the family, the DS2252T provides crashproof operation in portable systems or systems with unreliable power. These features include the ability to save the operating state, Power-fail Reset, Power-fail Interrupt, and Watchdog Timer. All nonvolatile memory and resources are maintained for over 10 years at room temperature in the absence of power.

A user loads programs into the DS2252T via its on-chip Serial Bootstrap Loader. This function supervises the loading of software into NV RAM, validates it, then becomes transparent to the user. It also manages the loading of new encryption keys automatically. Software is stored in onboard CMOS SRAM. Using its internal Partitioning, the DS2252T can divide a common RAM into user selectable program and data segments. This Partition can be selected at program loading time, but can be modified anytime later. The microcontroller will decode memory access to the SRAM, access memory via its Bytewide bus and write-protect the memory portion designated as program (ROM).

A detailed summary of the security features is provided in the User’s Guide section of the Secure Microcontroller data book. An overview is also available in the DS5002FP data sheet.

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DS2252T BLOCK DIAGRAM Figure 1

DS2252T

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PIN ASSIGNMENT

1 P1.0 11 P1.5 21 P3.1 TXD 31

DS2252T

P3.6 WR

3 P1.1 13 P1.6 23 4 P0.0 14 P0.5 24 5 P1.2 15 P1.7 25

12 P0.4 22 ALE 32 P2.4

P3.2 INT0

PROG

P3.3 INT1

P3.7 34 P2.3 35 XTAL2

6 P0.1 16 P0.6 26 P2.7 36 P2.2 7 P1.3 17 RST 27 P3.4 T0 37 XTAL1 8 P0.2 18 P0.7 28 P2.6 38 P2.1 9 P1.4 19 P3.0 RXD 29 P3.5 T1 39 GND 10 P0.3 20 SDI 30 P2.5 40 P2.0

PIN DESCRIPTION

4, 6, 8, 10, 12, 14, 16,

1, 3, 5, 7, 9, 11, 13,15P1.0 - P1.7. General purpose I/O Port 1.

P0.0 - P0.7. General purpose I/O Port 0. This port is open-drain and can not drive a logic

1. It requires external pullups. Port 0 is also the multiplexed Expanded Address/Data bus. When used in this mode, it does not require pullups.

40, 38, 36, 34, 32, 30,

28, 26

P2.0 - P2.7. General purpose I/O Port 2. Also serves as the MSB of the Expanded Address bus.

P3.0 RXD. General purpose I/O port pin 3.0. Also serves as the re ceive signal for the on board UART. This pin should NOT be connected directly to a PC COM port.

P3.1 TXD. General purpose I/O port pin 3.1. Also serves as the transmit signal for the on board UART. This pin should NOT be connected directly to a PC COM port.

P3.2

INT0 . General purpose I/O port pin 3.2. Also serves as the active low External

Interrupt 0. This pin is also connected to the INTP output of the DS1283 Real Time Clock.

P3.3 INT1. General purpose I/O port pin 3.3. Also serves as the active low External Interrupt 1.

27 P3.4 T0. General purpose I/O port pin 3.4. Also serves as the Timer 0 input. 29 P3.5 T1. General purpose I/O port pin 3.5. Also serves as the Timer 1 input.

P3.6 WR . General purpose I/O port pin. Also serves as the write strobe for Expanded bus operation.

RD. General purpose I/O port pin. Also serves as the read strobe for Expanded bus

P3.7

operation.

RST - Active high reset input. A logic 1 applied to this pin will activate a reset state. This pin is pulled down internally, can be left unconnected if not used. An RC power-on reset circuit is not needed and is NOT recommended.

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PIN DESCRIPTION

ALE - Address Latch Enable. Used to de-multiplex the multiplexed Expanded

Address/Data bus on Port 0. This pin is normally connected to the clock input on a ’373 type transparent latch.

DS2252T

35, 37

XTAL2, XTAL1. Used to connect an external crystal to the internal oscillator. XTAL1 is the input to an inverting amplifier and XTAL2 is the output.

39 GND - Logic ground.

2 VCC - +5V.

PROG - Invokes the Bootstrap loader on a falling ed ge. This signal should be debounced

so that only one edge is detected. If connected to ground, the microcontroller will enter Bootstrap loading on power up. This signal is pulled up internally.

SDI – Self-Destruct Input. A logic 1 applied to this input causes a hardware unlock. This

involves the destruction of Encryption Keys, Vector RAM, and the momentary removal of power from V

. This pin should be grounded if not used.

CCO

INSTRUCTION SET

The DS2252T executes an instruction set that is object code-compatible with the industry standard 8051 microcontroller. As a result, software development packages such as assemblers and compilers that have been written for the 8051 are compatible with the DS2252T. A complete description of the instruction set and operation are provided in the User’s Guide section of the Secure Microcontroller Data Book.

MEMORY ORGANIZATION

Figure 2 illustrates the memory map accessed by the DS2252T. The entire 64k of program and 64k of data are available to the Byte-wide bus. This preserves the I/O ports for application use. An alternate configuration allows dynamic Partitioning of a 64k space as shown in Figure 3. Any data area not mapped into the NV RAM is reached via the Expanded bus on P orts 0 and 2. Off-boa rd program memor y is not available for security reasons. Selecting PES=1 provides access to the Real Time Clock as shown in Figure 4. These selections are made using Special Function Registers. The memor y map and its controls are covered in detail in the User’s Guide section of the Secure Microcontroller Data Book.

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